Process for dehydrogenating



' butadiene-1,3.

United States Patent f 3,274,285 PROCESS FOR DEHYDROGENATING Laimoni'sBajars, Princeton, N.J., assignor to Petra-Tex Chemical Corporation,Houston, Tea, a corporation of Delaware No Drawing. Filed June 11, 1965,Ser. No. 463,372 16 Claims. (Cl. 260-680) This invention relates to aprocesss for dehydrogenating organic compounds. 7

This application is a continuation-in-part of my earlier filed copendingapplication Serial Number 244,276, filed December 13, 1962, entitledDehydrogenation Process, now US. Patent No. 3,207,111 which in turn wasa continuation-in-part of my earlier filed application Serial Number36,718, filed June 17, 1960, entitled Dehydrogenation Process, nowabandoned. This application also discloses subject matter disclosed inmy earlier filed and now abandoned applications Serial No. 145,992 andSerial No. 145,993, both filed October 18, 1961.

The invention is suitably carried out by passing a mixture in criticalproportions, of the compound to be dehydrogenated, chlorine or achlorine-liberating compound, and oxygen, at a temperature of at least450 C., and at an organic compound partial pressure equivalent to lessthan about one-fifth atmosphere at a total pressure of one atmosphere inthe presence of a cobalt catalyst, to obtain the correspondingunsaturated organic compound derivative of the same number of carbonatoms.

Suitable hydrocarbons to be dehydrogenated according to the process ofthis invention are aliphatic hydrocarbons of 4 to 6 carbon atoms andpreferably are selected from the group consisting of mono-olefins ordiolefins of 4 to 6 carbon atoms, saturated aliphatic hydrocarbons of 4to 6 carbon atoms and mixtures thereof. Examples of feed materials arebutene-l, cis-butene-2, trans-butene-Z, Z-methyl butene-3, Z-methylbutene-l, Z-methyl butene-Z, n-butane, isobutane, butadiene-L3, methylbutane, Z-methyl pentenel, 2-methyl pentene-Z and mixtures thereof. Forexample, n-butane may be converted to a mixture of butene-l and butene-2or may be converted to a mixture of butene-l, butene-2 and/or A mixtureof n-butane and butene-2 may be converted to butadiene-1,3 or a mixtureof butadiene- 1,3 together with some butene-2 and butene-l. n-Butane,butene-l, butene-2 or butadiene-1,3 or mixtures thereof may be convertedto vinyl acetylene. The reaction temperature for the production of vinylacetylene is normally within the range of about 600 C. to 1000 C., suchas between 650 C. and 850 C. Isobutane may be converted to isobutylene.The 2-methyl butenes such as 2-methyl butene-l may be converted toisoprene. Excellent starting materials are the four carbon hydrocarbonssuch as butene-l, cis or trans butene-2, n-butane, and butadiene-1,3 andmixtures thereof. Useful feeds as starting materials may be mixedhydrocarbon streams such as refinery streams. For example, the feedmaterial may be the olefin-containing hydrocarbon mixture obtained asthe product from the dehydrogenation of hydrocarbons. Another source offeed for the present process is from refinery by-products. For example,in the production of gasoline from higher hydrocarbons by either thermalor catalytic cracking a predominantly bydrocarbon stream containingpredominantly hydrocarbons of four carbon atoms may be produced and maycomprise a mixture of butenes together with butadiene, butane,isobutane, isobutyleue and other ingredients in minor amounts. These andother refinery by-p-roducts which contain normal ethylenicallyunsaturated hydrocarbons are useful as starting materials. Anothersource of feedstock is the product from the dehydrogenation of butane tobutenes employing the Houdry Process. Al-

3,274,285 Patented Sept. 20, 1966 though various mixtures ofhydrocarbons are useful, the preferred hydrocarbon feed contains atleast 50 weight percent butene-l, butene-Z, n-butane and/or butadiene-1,3 and mixtures thereof, and more preferably contains at least 70percent n-butane, butene-l, butene-2 and/ or butadiene-1,3, and mixturesthereof. Any remainder usually will be aliphatic hydrocarbons. Cyclichydrocarbons of 6 to 9 carbon atoms are also suitable but lesspreferred, such as the dehydrogenation of cyclohexane to cyclohexeneand/or benzene .and the dehydrogenation of ethyl benzene to styrene, andthe like. The process of this invention is particularly effective indehydrogenating aliphatic hydrocarbons having a straight carbon chain ofat least 4 carbon atoms to provide a product wherein the majorunsaturated product has the same number of carbon atoms as the feedhydrocarbon.

The chlorine-liberating material may be such as chlorine itself,hydrogen chloride, alkyl chlorides of 1 to 4 carbon atoms such as methylchloride or ethylene dichloride, carbon tetrachloride, ammoniumchloride, volatile metalloid chlorides, aromatic chlorides such asphenyl chloride, heterocyclic chloride, such as cyclohexyl chloride, andthe like. Preferably the chlorine-containing material will eithervolatilize or decompose at a temperature of no greater than C. toliberate the required amount of chlorine or hydrogen chloride. Theamount of chlorine must be at least 0001 or 0.005 mol, and usually anamount of at least 0.01 mol of chlorine per mol of organic compound tobe dehydrogenated will be used. It is one of the unexpected advantagesof this invention that only very small amounts of chlorine are required.Less than 0.5 mol of chlorine, as 0.2 mol, per mol of organic compoundto be dehydrogenated may be employed. Suitable ranges are such as fromabout .005 or 0.01 to 0.05, 0.1 or 0.25 mol of chlorine per 1101 of thecompound to be dehydrogenated. Excellent results are obtained when thechlorine is present in amount of less than 0.3 mol of chlorine per molof the compound to be dehydrogenated. It is understood that when aquantity of chlorine is referred to herein, both in the specificationand the claims, that this refers to the calculated quantity of chlorinein all forms present in the vapor space under conditions of reactionregardless of the initial source 'or the form in which the chlorine ispresent. For example, a reference to 0.05 mol of chlorine would refer tothe quantity of chlorine present whether the chlorine was fed as 0.05mol of C1 or 0.10 mol of HCl. Preferably, the chlorine will be presentin an amount no greater than 5 or 10 mol percent of the total feed tothe dehydrogenation zone, including any diluents.

The minimum amount of oxygen employed will generally be at least aboutone-fourth mol ofoxygen per mol of organic compound to bedehydrogenated. Large amounts as about 3 mols of oxygen per mol oforganic compound may be used. Excellent yields of the desiredunsaturated derivatives have been obtained with amounts of oxygen fromabout 0.4 to about 1.0 or 1.5 mols of oxygen per mol of organic compoundand suitably may 7 be within the range of about 0.4 to 2 mols of oxygenper mol of organic compound. Preferably, the oxygen will be present inan amount of a least 0.6 mol per mol of compound to be dehydrogenated.Oxygen may be supplied to the reaction system as oxygen diluted withinert gases such as helium, carbon dioxide, as air and the like. Inrelation to chlorine, the amount of oxygen employed should be greaterthan 1.50 gram mols of oxygen per gram atom of chlorine present in thereaction mixture. Usually the ra-tio of the mols of oxygen to the molsof chlorine will be greater than 4 or 5 mols of oxygen per I mol ofchlorine, such as between 6 or 8 and 500 or about 15 and 300 mols ofoxygen per mol of chlorine.

The total pressure on systems employing the process of this inventionnormally will be at or in excess of atmospheric pressure but vacuum maybe used. Higher pressures, such as about 100 or 200 p.s.i.g. may beused. The initial partial pressure of the organic compound to bedehydrogenated under reaction conditions is critical and is preferablyequivalent to below about one-fifth atmosphere (or about 6 inches ofmercury absolute) when the total pressure is atmospheric to realize theadvantages of this invention and more preferably equivalent to nogreater than 3 or 4 inches of mercury absolute. Also, because theinitial partial pressure of the hydrocarbon to be dehydrogenated isequivalent to less than about 6 inches of mercury at a total pressure ofone atmosphere, the combined partial pressure of the hydrocarbon to bedehydrogenated plus the dehydrogenated hydrocarbon will also beequivalent to less than about 6 inches of mercury. For example, ifbutene is being dehydrogenated to butadiene, at no time will thecombined partial pressure of the butene and butadiene be greater thanequivalent to about 6 inches of mercury at a total pressure of oneatmosphere. The desired pressure is obtained and maintained bytechniques including vacuum operations, or by using helium, organiccompounds, nitrogen, steam and the like, or by a combination of thesemethods. Steam is particularly advantageous and it is surprising thatthe desired reactions to produce high yields of product are effected inthe presence of large amounts of steam. When steam is employed, theratio of steam to hydrocarbon to be dehydrogenated is normally withinthe range of about 4 or to 20 or 30 mols of steam per mol ofhydrocarbon, and generally will be between 8 and mols of steam per molof hydrocarbon. The degree of dilution of the reactants with steam,nitrogen and the like is related to keeping the partial pressure ofhydrocarbon to be dehydrogenated in the system equivalent to prefer-ablybelow 6 inches of mercury at one atmosphere total pressure. For example,in a mixture of one mol of butene, three mol-s of steam and one mol ofoxygen under a total pressure of one atmosphere, the butene would havean absolute pressure of one-fifth of the total pressure, or roughly sixinches of mercury absolute pressure. Equivalent to this six inches ofmercury butene absolute pressure at atmospheric pressure would be butenemixed with oxygen and chlorine under a vacuum such that the partialpressure of the butene is six inches of mercury absolute. A combinationof a diluent such as steam together with a vacuum may be utilized toachieve the desired partial pressure of the hydrocarbon. For the purposeof this invention, also equivalent to the six inches of mercury buteneabsolute pressure at atmospheric pressure would be the same mixture ofone mol of butene, three mols of steam and one mol of oxygen under atotal pressure greater than atmospheric, for example, a total pressureof 15 or inches mercury above atmospheric. Thus, when the total pressureon the reaction zone is greater than one atmosphere, the absolute valuesfor the pressure of butene will be increased in direct proportion to theincrease in total pressure above one atmosphere. Another feature of thisinvention is that the combined partial pressure of the hydrocarbon to bedehydrogenated plus the chlorine-liberating material will also beequivalent to less than 6 inches of mercury, and preferably no greaterthan 3 or 4 inches of mercury, at a total pressure of one atmosphere.The lower limit of hydrocarbon partial pressure will be dictated bycommercial considerations and practically will be greater than about 0.1inch mercury.

The temperature of reaction may be at least 450 C. and preferably willbe at least about 500 C. The temperature of the reaction is from about450 C. to temperatures as high as 850 C. or 1000 C. The optimumtemperature is normally determined as by thermocouple at the maximumtemperature of the reaction. Usually the temperature of reaction will befrom at least or greater than 450 C. to about 750 C. or 900 C. Excellentreequivalent to the mols of feed mixture.

4 sults have been obtained in the range of about 550 C. to 750 C., or500 C. to 850 C. At the higher temperatures vinyl acetylene may beproduced from 4 carbon hydrocarbon feed such as butene or butadiene. Thetemperatures are measured at the maximum temperature in the reactor.

The flow rates of the gaseous reactants may be varied quite widely andorganic compound gaseous flow rates ranging from about 0.1 to about 5liquid volumes of organic compound per volume of reactor packing perhour have been used. Generally, the flow rates will be within the rangeof about 0.10 to 25 or higher liquid volumes of the compound to bedehydrogenated, calculated at standard conditions of 0 C. and 760 mm. ofmercury per volume of reactor space containing catalyst per hour(referred to as either LHSV or liquid v./v./hr.). Usually the LHSV willbe between 0.15 and 15. The volume of reactor containing catalyst isthat volume of reactor space including the volume displaced by thecatalyst. For example, if a reactor has a particular volume of cubicfeet of void space, when that void space is filled with catalystparticles, the original void space is the volume of reactor containingcatalyst for the purpose of calculating the flow rates. The residence orcontact time of the react-ants in the reaction zone under any given setof reaction conditions depends upon the factors involved in thereaction. Contact times ranging from about 0.001 or 0.01 to about onesecond or higher, such as 5 or 10 or 20 seconds, have been found to besatisfactory. A preferred range is from 0.001 to 5 seconds. Residencetime is the calculated dwell time of the reaction mixture in thereaction zone, assuming the mols of production mixture are For thepurpose of calculation of residence times, the reaction zone is theportion of the reactor containing catalyst.

The manner of mixing the chlorine or chlorine-liberating compound,organic compound to be dehydrogenated, oxygen containing gas, and steam,if employed, is subject to some choice. In normal operations, theorganic compound may be preheated and mixed with steam and preheatedoxygen or air, and chlorine or hydrogen chloride are mixed therewithprior to passing the stream in vapor phase over the catalyst bed.Hydrogen chloride or a source of chlorine may be dissolved in water andmay be mixed with steam or air prior to reaction. Any of the reactantsmay be split and added incrementally. For example, part of the chlorinematerial may be mixed with the hydrocarbon to be dehydrogenated and theoxygen. The mixture may then be heated to effect some dehydrogenationand thereafter the remainder of the chlorine material added to effectfurther dehydrogenation. The hydrocarbon product is then suitablypurified as by fractionation to obtain the desired high purityunsaturated product.

For conducting the reaction, a variety of reactor types may be employed.Fixed bed reactors may be used and fluid and moving bed systems areadvantageously applied to the process of this invention. In any of thereactors suitable means for heat removal may be provided. Tubularreactors of small diameter may be employed and large diameter reactorswhich are loaded or packed with packing materials are very satisfactory.

Excellent results have been obtained by packing the reactor with thedefined catalyst particles as the method of introducing the catalyticsurface. The size of the catalyst particles may vary widely butgenerally the maximum particle size will at least pass through a TylerStandard Screen which has an opening of 2 inches, and generally thelargest particles of catalyst will pass through a Tyler Screen with oneinch openings. Very small particle size carriers may be utilized withthe only practical objection being that extremely small particles causeexcessive pres sure drops across the reactor. In order to avoid highpressure drops across the reactor, generally at least 50 percent byweight of the catalyst will be retained by a 10 mesh Tyler StandardScreen which 'has openings of inch. However, if a fluid bed reactor isutilized, catalyst particles may be quite small, such as from about to300 microns. Thus, the particle size when particles are used preferablywill be from about 10 microns to a particle size which will pass througha Tyler Screen with openings of 2 inches. If a carrier is use-d, thecatalyst may be deposited on the carrier by methods known in the artsuch as by preparing an aqueous solution or dispersion of the describedcatalyst, mixing the carrier with the solution or dispersion until theactive ingredients are coated on the carrier. The coated particles maythen be dried, for example, in an oven at about 110 C. Various othermethods of catalyst preparation known to those skilled in the art may beused. When carriers are utilized, these will be approximately of thesame size as the final coated catalyst particle, that is, for fixed bedprocesses the carriers will generally be retained on 10 mesh TylerScreen and will pass through a Tyler Screen With openings of 2 inches.Very useful carriers are Alundum, silicon carbide, Carborundum, pumice,kieselguhr, asbestos, and the like. The Alundums or other aluminacarriers are particularly useful. When carriers are used, the amount ofcatalyst on the carrier will generally be in the range of about 5 to 75weight percent of the total weight of the active catalytic material pluscarrier. The carriers may be of a variety of shapes, including irregularshapes, cylinders or spheres. Another method for introducing therequired surface is to utilize as a reactor a small diameter tubewherein the tube wall is catalytic or is coated with catalyticmate-rial. If the tube wall is the only source of catalyst generally thetube wall will be of an internal diameter of no greater than one inchsuch as less than 4 inch in diameter or preferably will be no greaterthan about /2 inch in diameter. Other methods may be utilized tointroduce the catalytic surface such as by the use of rods, wires, meshor shreds and the like of catalytic material. The technique of utilizingfluid beds lends itself well to the process of this invention.

In the descriptions below of catalyst compositions, the compositiondescribed is that of the surface which is exposed in the dehydrogenationzone to the reactants. That is, if a catalyst carrier is used, thecomposition described as the catalyst refers to the composition of thesurface and not to the total composition of the surface coating pluscarrier. The catalytic compositions are intimate combinations ormixtures of the ingredients. These ingredients may or may not bechemically combined or alloyed. Inert catalyst binding agents or fillersmay be used, but these will not ordinarily exceed about 50 percent or 65percent by weight of the catalytic surface exposed to the reactiongases.

' The amount of solid catalyst utilized may be varied depending uponsuch variables as the activity of the catalyst, the amount of chlorineand oxygen used, the flow rates of reactants and the temperature ofreaction. The amount of catalyst will be present in an amount of greaterthan 25 square feet of catalyst surface per cubic foot of reaction zonecontaining catalyst. Generally the ratios will be at least 40 squarefeet of catalyst surface per cubic foot of reaction zone. The catalystis more effectively utilized when the catalyst is present in an amountof at least 75 square feet of catalyst surface per cubic foot ofreaction zone containing catalyst, and preferably the ratio of catalystsurface to volume will be at least 120 square feet of catalyst surfaceper cubic foot of reaction zone containing catalyst. Of course, theamount of catalyst surface may be much greater when irregular surfacecatalysts are used. When the catalyst is in the form of particles,either supported or unsupported, the amount of catalyst surface may beexpressed in terms of the surface area per unit weight of any particularvolume of catalyst particles. The ratio of catalytic surface to weightwill be dependent upon various factors including the particle size,particle distribution, apparent bulk density of the particles, amount ofactive catalyst coated on the carrier, density of the carrier, and soforth. Typical values for the surface to Weight ratio are such as about/2 to 200 square meters per gram although higher and lower values may beused.

The catalyst of this invention will be cobalt or a cobalt compound andmixtures thereof. Cobalt metal and compounds thereof such as the salts,oxides, or hydroxides are effective catalysts. Particularly effectiveare inorganic compounds such as the oxides, phosphates, and the halides,such as the iodides, bromides, chlorides and fluorides. Useful catalystsare such as cobaltic oxide, cc'baltous oxide, cobalt metal, Co(C H O(decomposes), Co Br CoCl CoF C0 0 cobalt phosphate, CoP ,CoSO and thelike. Mixtures of the cobalt or cobalt compounds may be used. Alsomixtures of salts, such as halides, and oxides may be employed.Preferably, the catalyst will be solid under the conditions of reaction.The preferred catalyst is cobalt oxide. Many of the salts and hydroxidesof cobalt may change during the preparation of the catalyst, duringheating in a reactor prior to use in the process of this invention, orare converted to another form under the described reaction conditions,but such materials still function as an effective compound in thedefined process. For example, cobalt nitrate or acetate, and the like,may be converted to the corresponding oxide or chloride under thereaction conditions defined herein. Salts which may be stable orpartially stable at the defined reaction temperatures are likewiseeffective under the conditions of the described reaction, as well assuch compounds which are converted to another form in the reactor. Atany rate, the catalysts are effective if cobalt is present in acatalytic amount in contact with the reaction gases. The cobalt oxidesrepresent a preferred class of materials. The catalysts of thisinvention are solid at room temperature or are slightly solid under theconditions of reaction (although some volatilization may occur).

In the following examples will be found specific embodiments of theinvention and details employed in the practice of the invention. LHSV(or liquid v./v./hr.) means, with reference to the flow rate of organiccompound to be dehydrogenated, liquid volume of organic compound perhour per volume of packing or active surface material in the reactionzone. Percent conversion represents mols of organic compound consumedper mols of organic compound fed to a reactor and percent selectivityrepresents the mols of defined unsaturated organic derivative thereofformed per 100 mols of organic compound consumed. These examples areintended as illustrative only since numerous modifications andvariations in accordance with the disclosure herein Will be apparent tothose skilled in the art. All quantities of chlorine expressed arecalculated as mols of C1 n-Butane is dehydrogenated in a series of runsutilizing various catalysts. The runs are made in a one-inch diameterVycor reactor. The overall length of the reactor is approximately 14inches, and 12 inches of the center portion of the reactor is surroundedby an electrical heating furnace. At the bottom of the reactor areplaced a few A" x A" Vycor Raschig rings. On top of the Raschig rings,and within the portion of the reactor surrounded by the heating furnace,is placed 50 cc. of the designated catalyst. The remainder of thereactor is filled with A" x A" Vycor Raschig rings to form a preheatzone. The flow of the gases through the reactor is from the top to thebottom. The various catalysts are present in the reactor deposited on Adiameter alumina spheres as supports (Norton Co. SA-5218). Unless in- Asmeasured by the Innes nitrogen absorption method on a representativeunit volume of catalyst particles. The Innes is reported in Innes, W.B.,Anal. Chem., 23, 759

2 Vycor is the trade name of Corning Glass Works, Corning, N.Y., and iscomposed of approximately 96 percent silica with the remainder beingessentially B 0 dicated otherwise, the catalyst is present as the oxide.The cobalt compound to be used as a catalyst is slurried in distilledwater, and the Vycor Raschig rings to be used as the carrier areimmersed in the slurry in order to form the coating. The combination ofthe carrier and the slurry is heated in a rotating glass beaker which issurrounded by a heater. The particles are tumbled and heated until thecatalyst particles are dry enough to flow freely. The maximumtemperature of the catalyst particles in this heater is no greater thanapproximately 100 C. Thereafter, the catalyst particles are transferredto an oven and heated at about 150 C. to further dry the particles(approximately 4 hours).

The runs are made at an oxygen to butane ratio of 1.30 mols of oxygen(fed as air) per mol of butane and at a chlorine to butane ratio of 0.30mol C1 (fed as chlorine). Nitrogen is present in the feed in an amountof 15 mols per mol of butane. The flow rate of butane is .25 liquidhourly space velocity. The maximum temperature in the reactor is 550 C.Under these conditions and utilizing a C 0 catalyst, 79.3 mol percent ofthe n-butane is converted to a mixture of n-butene and butadiene-1,3 ata total selectivity of about 60 mol percent. Only a minor amount ofchlorinated and heavier hydrocarbons are produced. When the run isrepeated substituting cobalt phosphide, cobalt sulfate, cobalt (II)fluoride, cobalt acetate or cobalt (II) chloride, similarly high yieldsare obtained. When n-butene-2 or 2-methy1 butene-2 is substituted forthe n-butane, high yields of the corresponding diolefins of the samenumber of carbon atoms are obtained.

From the foregoing description of the invention, it will be seen that anovel and greatly improved process is provided for producing unsaturatedcompounds of lower molecular weight but of the same number of carbonatoms as the feed. Other examples could be devised for a process wherebythe catalyst contained the described elements, preferably with thedescribed elements constituting greater than or at lea-st fifty atomicweight percent of any cations in the surface exposed to the reactiongases. Excellent catalysts are obtained when the defined catalyticmaterials are the main active constituent in the catalyst. Also, thecatalyst may consist essentially of the defined catalyticmaterials.Although representative embodiments of the invention have beenspecifically described, it is not intended or desired that the inventionbe limited solely thereto since it will be apparent to those skilled inthe art that modifications and variations may be made without departingfrom the spirit and scope of the invention. The products such asbutadiene-1,3 have many well known uses such as raw materials for theproduction of synthetic rubber.

I claim:

1. The method for dehydrogenating aliphatic hydrocarbons of 4 to 6carbon atoms which comprises heating in the vapor phase at a temperatureof from about 450 C. to 850 C. an aliphatic hydrocarbon of 4 to 6 carbonatoms with oxygen in a molar ratio of at least one-fourth mol of oxygenper mol of said hydrocarbon and chlorine in a molar ratio of less than0.5 mol of chlorine per mol of said hydrocarbon, the partial pressure ofsaid hydrocarbon being equivalent to less than about one-fifthatmosphere at a total pressure of one atmosphere, with a materialselected from the group consisting of metals, salts, oxides andhydroxides of cobalt and mixtures thereof in a catalytic amount, theratio of the gram mols of the said oxygen to the gram atoms of saidchlorine being at least 1.50,

2. The method of claim 1 wherein the said hydrocar-' 5. The method ofclaim 1 wherein the said hydrocarbon comprises n-butane.

6. The method of claim 1 wherein the oxygen is present in an amount offrom about 0.4 to 2 mols of oxygen per mol of said hydrocarbon.

7. The method of claim 1 wherein the chlorine is present in an amount offrom at least 0.01 mol of chlorine to 0.2 mol of chlorine per mol ofsaid hydrocarbon.

8. The method of claim 1 wherein the said material has as its mainactive constituent the said metals, salts, oxides and hydroxides ofcobalt and mixtures thereof.

9. The method of claim 1 wherein the vapor phase contains from about 4to 30 mols of steam per mol of said hydrocarbon.

10. The method of claim 1 wherein the cobalt is present as an oxide.

11. The method of claim 1 wherein the cobalt is present as a chloride.

12. The method of claim 1 wherein the cobalt is present as an inorganicsalt.

13. The method for dehydrogenating acyclic hydrocarbons of 4 to 5 carbonatoms which comprises heating in the vapor phase at a temperature offrom about 450 C. to 850 C. the corresponding acyclic hydrocarbon of 4to 5 carbon atoms with oxygen in a molar ratio of from about 0.4 to 2mols of oxygen per mol of said acyclic hydrocarbon and chlorine in amolar ratio of from at least 0.01 mol of chlorine to 0.2 mol of chlorineper mol of said hydrocarbon, the partial pressure of said hydrocarbonbeing equivalent to less than about one-fifth atmosphere at a totalpressure of one atmosphere, in the presence of a catalyst comprisingcobalt in an amount greater than fifty atomic weight percent of anycations in the catalyst surface exposed to the reaction gases, the ratioof the gram mols of the said oxygen to the gram atoms of said chlorinebeing at least 1.50.

14. The method of claim 13 wherein the said catalyst comprise-s cobaltoxide as its main active constituent.

15. The method of claim 13 wherein the said hydrocarbon comprise-sn-butane. v

16. The method of dehydrogenation of n-butene-2 which comprises heatingin the vapor phase at a temperature of about 550 C. to 750 C. butene-2with oxygen in an amount of about 0.85 mol of oxygen per mol of butene-2and about 0.115 mol of chlorine per mol of hutene-2 and about 16 mols ofsteam per mol of butene-2 with cobalt oxide.

References Cited by the Examiner UNITED STATES PATENTS 2,370,513 2/1945Amos et a1. 260680 2,833,832 5/1958 Fox 260666 2,971,995 2/1961Arganbright 260--683.3 3,028,440 4/ 1962 Arg-anbright 260680 3,173,9623/1965 Carroll et al 260680 3,205,280 9/1965 Wattimena et al 260680 PAULM. COUGHLAN, JR., Primary Examiner,

1. THE METHOD FOR DEHYDROGENATING ALIPHATIC HYDROCARBON OF 4 TO 6 CARBONATOMS WHICH COMPRISES HEATING IN THE VAPOR PHASE AT A TEMPERATURE OFFROM ABOUT 450* C. TO 850*C. AN ALIPHATIC HYDROCARBON OF 4 TO 6 CARBONATOMS WITH OXYGEN IN A MOLAR RATIO OF AT LEAST ONE-FOURTH MOL OF OXYGENPER MOL OF SAID HYDROCARBON AND CHLORINE IN A MOLAR RATIO OF LESS THAN0.5 MOL OF CHLORINE PER MOL OF SAID HYDROCARBON, THE PARTIAL PRESSURE OFSAID HYDROCARBON BEING EQUIVALENT TO LESS THAN ABOUT ONE-FIFTHATMOSPHERE AT A TOTAL PRESSURE OF ONE ATMOSPHERE, WITH A MATERIALSELECTED FROM THE GROUP CONSISTING OF METALS, SALTS, OXIDES ANDHYDROXIDES OF COBALT AND MIXTURES THEREOF IN A CATALYTIC AMOUNT, THERATIO OF THE GRAM MOLS OF THE SAID OXYGEN TO THE GRAM ATOMS OF SAIDCHLORINE BEING AT LEAST 1.50.